1. Field of the Invention
The invention pertains to a method at least for reading analog and/or digital data stored on a microform by the use of a device for accessing the microform which is connected to a data processing system by a hardware interface. The invention also pertains to a device for implementing the method and to a microform.
2. Description of the Prior Art
Microforms (microfilm, microfiche, and aperture cards) have been used since 1920 for the archival of documents. The number of microfiches alone existing in the world today is estimated at several billion. There are also a correspondingly large number of reading devices on the market. These are characterized in that the content stored on the microform is either presented to the observer directly on a matte glass screen or scanned by electronic methods and made visible by digitizing equipment.
Most of the data stored on microforms in the past has been in the form of copies of image and/or text documents. Conventional microfiches for storing analog data are usually designed according to the method described in DIN ISO 9923. The microfiche, which measures 105 mm×148 mm, is divided into two areas. The first area is reserved for a title field, which can be read by man and/or device. The second area is divided into a varying numbers of fields, each of which contains a reduced-size representation of any desired document in shades of gray (analog data). As listed in Table 1 below, the number of fields, depending on how the microfiche is divided, varies between 1 and 420:
TABLE 1Division of a microfiche according to DIN ISO 9923.Maxima 1Number ofImageDimensions ofNumberNumber ofWidth ofLowerLeftImageImage FieldsSize1)Image Field2)of RowsColumnsTitle FieldEdgeEdgeNo.4987.5 × 14012.5 × 20  7712.254 ± 0.54 ± 0.539887.5 × 140  10 × 12.571412.254 ± 0.54 ± 0.53270 93.75 × 139.56.25 × 7.75151864 ± 0.54 ± 0.5442093.75 × 140   5 × 6.25152864 ± 0.54 ± 0.551  95 × 133 95 × 133——8.250.5 ± 0.20 7.5 ± 0.25 61)The image size does not include the title field.2)Single fields and double fields may be used on the same microfiche.
EP 1 684 199 A2 discloses a method for digitizing and displaying analog data stored on microfiches, in which the digitized data are sent to a text recognition software program. The digital data generated by the text recognition process are subjected to further processing in a data processing system.
DE 40 00 671 A1 discloses the use of microfilm as a storage medium for data. The data are stored as alphanumeric symbols on the microfilm in analog fashion. The microfilm is laid in a computer input microfilm reader, which scans the microfilm and converts the symbols stored in the microfilm into computer data. Text recognition software is used here, too, to accomplish the conversion. The text recognition process results in computer codes, which correspond to the symbols on the microfilm. These computer codes are transmitted by the reader to a data processing system via a computer interface.
U.S. Pat. No. 4,213,040 A describes a microfiche, on which digital or analog data are stored; the data are read by a scanner and sent as output via an interface to electronic circuits, which process the digital or analog data. The digital data are arranged line by line down the length of the microfiche card. Above and below the data area there is in each case an incremental code, which is evaluated by a scanner and a logic circuit. If the bits of the incremental upper and lower codes do not agree bit for bit, the sensor is aligned by the logic circuit, so that the data in their line-by-line arrangement can be read out correctly. In addition, the microfiche also has a horizontal bar above and another one below the data area; these bars mark the beginning and the end of the data. In the areas above and below the data area, furthermore, there are also centering marks, which are aligned with the data, which are arranged in rows and columns. The centering marks make it possible for the data to be addressed, the data within the data area always being in read out in their entirety.
One the main disadvantages of the known methods and devices for accessing microforms is that the data acquired by the scanners can be subjected to further processing only by special electronic circuits or in data processing systems equipped with special software. In addition, the known methods and devices allow access either only to microforms with analog data or only to microforms with digital data. Finally, the known digital microforms are not suitable for rapid access to the data.